Forty-year-old migrant worker Li Hai thought his chance to get-rich-quick had arrived when he saw the tabloid advertisement: "Rich woman willing to pay 3 million yuan for sperm donor."

Li instantly contacted the dating agency mentioned in the ad - a move that ended in his being cheated out of 190,000 yuan ($27,500) in Chongqing municipality's biggest-ever dating fraud.

But Li was by no means the first to fall foul of this type of crime. The police department of Jiangbei district, Chongqing said on June 26 that more than 1,000 men from 25 provinces and municipalities had been lured into paying millions of yuan under similar circumstances, according to the Chongqing Evening News.

Police arrested 22 suspects, including the two masterminds of the scam who formerly ran an advertising agency and opened the bogus dating agency last July, various team leaders and 17 migrant and laid-off women workers who enacted the roles of millionairesses.

Police found evidence in the agency office that the couple had more than 3 million yuan in cash, $100,000 in futures, six houses and a car - a total wealth of 10 million yuan, all of which was allegedly defrauded from more than 1,000 men in 25 of China's provincial regions.

The bogus dating agency was discovered through the bank account transactions of 40-year-old Li Hai from Henan province. Li called the agency in January after seeing the advertisement and expressing willingness to be a donor. A woman pretending to be a counselor at a fictitious Chongqing marriage bureau told him to deposit 1,000 yuan in a specific bank account.

It was after Li paid the required amount that he began to talk on the phone to the so-called wealthy woman he was introduced to under the false name of Liu Fang. The agency told him he would need to deposit more funds if he wanted further contact with the woman, the newspaper said.

The man called Jiangbei criminal police when, after he had transferred more than 190,000 yuan to the account, both the woman and the agency disappeared.

The cash remittance slips that Li provided, recording daily cash withdrawals from the ATM at around 5 or 6 pm, were a vital clue in the investigation.

Police kept a close eye on all 11 ATMs in Jiangbei district and finally took five suspects into custody on April 7. The remaining 17 suspects were later arrested.

Upon paying an introduction fee, match-seekers were required to shell out further large amounts, purportedly for tax and guarantees, air tickets for face-to-face meetings, and birthday gifts, police said.

Chongqing police say that marriage fraud has escalated to the extent of becoming a public nuisance. A full 7,500 such scams were reported last year alone.

Jiangbei police told China Daily that as more than half of the crimes committed last year were street felonies such as cheating, minor robbery and pick pocketing, they established a street crime investigation unit on March 23.

Police warn citizens that a charming photograph is the initial step to sweet-talking men out of all their money, whose recipients then disappear into thin air.